﻿using System;
using System.Data;
using System.Configuration;
using System.Collections.Generic;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Reflection;
using System.IO;
using System.Data.Odbc;
namespace iSun.WebApp.Extend.Common
{
    /// <summary>
    /// 定义UI公用方法
    /// </summary>
    public class ExcelHelper
    {

            #region Fields
            string _fileName;
            DataTable _dataSource;//数据源
            string[] _titles = null;//列标题
            string[] _fields = null;//字段名

            #endregion

            #region .ctor
            /// <summary> 
            /// 构造函数 
            /// </summary> 
            /// <param name="dataSource">数据源</param> 
            public ExcelHelper()
            {

            }

            /// <summary> 
            /// 构造函数 
            /// </summary> 
            /// <param name="titles">要输出到 Excel 的列标题的数组</param> 
            /// <param name="fields">要输出到 Excel 的字段名称数组</param> 
            /// <param name="dataSource">数据源</param> 
            public ExcelHelper(string[] titles, string[] fields, DataTable dataSource)
                : this(titles, dataSource)
            {
                if (fields == null || fields.Length == 0)
                    throw new ArgumentNullException("fields");
                if (titles.Length != fields.Length)
                    throw new ArgumentException("titles.Length != fields.Length", "fields");

                _fields = fields;
            }

            /// <summary> 
            /// 构造函数 
            /// </summary> 
            /// <param name="titles">要输出到 Excel 的列标题的数组</param> 
            /// <param name="dataSource">数据源</param> 
            public ExcelHelper(string[] titles, DataTable dataSource)
                : this(dataSource)
            {
                if (titles == null || titles.Length == 0)
                    throw new ArgumentNullException("titles");

                _titles = titles;
            }

            /// <summary> 
            /// 构造函数 
            /// </summary> 
            /// <param name="dataSource">数据源</param> 
            public ExcelHelper(DataTable dataSource)
            {
                if (dataSource == null)
                    throw new ArgumentNullException("dataSource");
                // maybe more checks needed here (IEnumerable, IList, IListSource, ) ??? 
                // 很难判断，先简单的使用 DataTable 

                _dataSource = dataSource;
            }

            #endregion

            #region public Methods

            #region  导出到CSV文件并且提示下载
            /// <summary>
            /// 导出到CSV文件并且提示下载
            /// </summary>
            /// <param name="fileName"></param>
            public void DataToCSV(string fileName)
            {
                // 确保有一个合法的输出文件名 
                if (_fileName == null || _fileName == string.Empty || !(_fileName.ToLower().EndsWith(".xls")))
                    _fileName = GetRandomFileName();
                string data = ExportCSV();
                HttpContext.Current.Response.ClearHeaders();
                HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.Expires = 0;
                HttpContext.Current.Response.BufferOutput = true;
                HttpContext.Current.Response.Charset = "GB2312";
                HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");
                HttpContext.Current.Response.AppendHeader("Content-Disposition", string.Format("attachment;filename={0}.csv", System.Web.HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8)));
                HttpContext.Current.Response.ContentType = "text/h323;charset=gbk";
                HttpContext.Current.Response.Write(data);
                HttpContext.Current.Response.End();
            }

            #endregion
            #endregion

            #region 返回写入CSV的字符串
            /// <summary>
            /// 返回写入CSV的字符串
            /// </summary>
            /// <returns></returns>
            private string ExportCSV()
            {
                if (_dataSource == null)
                    throw new ArgumentNullException("dataSource");

                StringBuilder strbData = new StringBuilder();
                if (_titles == null)
                {
                    //添加列名
                    foreach (DataColumn column in _dataSource.Columns)
                    {
                        strbData.Append(column.ColumnName + ",");
                    }
                    strbData.Append("\n");
                    foreach (DataRow dr in _dataSource.Rows)
                    {
                        for (int i = 0; i < _dataSource.Columns.Count; i++)
                        {
                            strbData.Append(dr[i].ToString() + ",");
                        }
                        strbData.Append("\n");
                    }
                    return strbData.ToString();
                }
                else
                {
                    for (int j = 0; j< _titles.Length; j++)
                    {
                        strbData.Append(_titles[j] + ",");
                    }
                    strbData.Append("\n");
                    if (_fields == null)
                    {
                        foreach (DataRow dr in _dataSource.Rows)
                        {
                            for (int i = 1; i < _dataSource.Columns.Count; i++)
                            {
                                strbData.Append(dr[i].ToString() + ",");
                            }
                            strbData.Append("\n");
                        }
                        return strbData.ToString();
                    }
                    else
                    {
                        foreach (DataRow dr in _dataSource.Rows)
                        {
                            for (int i = 0; i < _fields.Length; i++)
                            {
                                strbData.Append(dr[_fields[i].ToString()].ToString() + ",");
                            }
                            strbData.Append("\n");
                        }
                        return strbData.ToString();
                    }
                }
            }
            #endregion

            #region 得到一个随意的文件名
            /// <summary> 
            /// 得到一个随意的文件名 
            /// </summary> 
            /// <returns></returns> 
            private string GetRandomFileName()
            {
                Random rnd = new Random((int)(DateTime.Now.Ticks));
                string s = rnd.Next(Int32.MaxValue).ToString();
                return DateTime.Now.ToShortDateString() + "_" + s + ".csv";
            }
            #endregion
    }
}